Free Web Analytics / Competitive Analysis tools

Are you availing of services like Quantcast, Compete.com and Google Trends for Websites? How about Google Analytics, Quantcast, NuConomy, Woopra and Piwik? Which ones and why?

Given the number of tools available, primarily at no-charge, businesses have unprecedeted access to data about how much and from where their visitors come and what they look at or how long.

With all this good data, inventory management remains an issue. trend-spotting remains an issue: i want intel from all these sources, and maybe others, to help me figure out where I might be next week or next month.

There must be tools that do this – I’ve used at least two and created others for clients over the years.

Where are the inventory management tools? The sales projection tools? The seasonality and trend-spotting tools, available gratis or otherwise?